Recent advances in the in silico modeling of cellular dynamics now permit explicit analysis of cellular structure formation. This provides the scientific community with the capability of testing hypotheses in precisely controlled environments for the first time. We describe an agent-based approach that simulates cells that reproduce, migrate and change shape. We find that both expected morphologies and previously unreported patterns spontaneously self-assemble. Most of the states found computationally have been observed in vitro, and it remains to be established what role these self-assembled states may play in in vivo morphogenesis.